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Cellular Respiration
7.3
Aerobic Respiration
Stages Aerobic Respiration
1.
2.
3.
4.


Stage 1:
Stage 2:
Stage 3:
Stage 4:
Glycolysis
Pyruvate Oxidation
Krebs Cycle
Electron Transport Chain and Chemiosmosis
Glycolysis occurs in cytoplasm
Stage 2 – 4 occurs in mitochondria
- possess double membrane: outer membrane as well as
an inner membrane (highly folded)
- intermembrane space between both membranes (fluid
filled)
- inner membrane contains mitochondrial matrix
(protein-rich liquid that fills interior)
Aerobic cellular respiration: Overview
Aerobic respiration: An overview
A series of enzyme controlled reactions
 Oxygen is used to oxidize glucose
 Glucose is oxidized to form carbon dioxide
 Oxygen is reduced to form water
During the oxidation of glucose:
 Electrons transferred to electron carriers, NAD+
and FAD+
 Glycolysis and Kreb’s cycle
 Electrons then passed through an electron
transport chain.
 The energy from the electrons will be used to
pump protons.
 The energy from the diffusion of protons will be
used to make ATP.
Stage 2: Pyruvate Oxidation
 Recall: reactions of glycolysis produced TWO
pyruvates, TWO ATP’s, and 2 NADH’s
- does not require O2 ; occurs in cytoplasm
 Pyruvate Oxidation: chemical pathway that connects
glycolysis to Krebs cycle
 2 pyruvate molecules are moved from the cytoplasm
to the matrix of the mitochondria
 CO2 is removed from each pyruvate molecule and
released as a waste product (1/3 of what you
exhale)
Stage 2: Pyruvate Oxidation Cont.
 The remaining 2-carbon
portions are oxidized by
NAD+; As a result, the NAD+
molecule gains two hydrogen
atoms and the remaining 2carbon molecule becomes
acetic acid
 Coenzyme A (Co-A) attaches
and forms acetyl-CoA
 Acetyl-coA enters stage 3
(Krebs cycle) and NADH
goes to stage 4 (ETC)
 2 CO2 diffuses out of the
mitochondria and cell.
Stage 3: Krebs Cycle
 This is an 8 step and cyclic stage
 cyclic because one of the products of step 8, is a
reactant in step 1
 At the end of the Krebs Cycle, all six carbons have
been oxidized to CO2 and released from the cell as
metabolic waste
 All that remains is some free energy in the form of
ATP and high energy NADH and FADH2
 These energy carriers enter the ETC
Krebs Cycle: The Details
Cycle occurs twice for each acetyl-CoA molecule
Acetyl CoA adds 2-carbons to oxaloacetate,
producing citrate
3. Citrate loses a CO2 molecule, and the resulting
compound is oxidized, reducing NAD+
to NADH
4. Another CO2 is lost, and the resulting compound is
oxidized, reducing NAD+ to NADH
5. ADP is phosphorylated to ATP
6. Two hydrogen's are transferred to FAD+ to form
FADH2
Kreb Cycle
1.
2.
Krebs Cycle Overview
1 Glucose=
2 ATP
6 NADH
2 FADH2
4 CO2
EACH pyruvate molecule produced in glycolysis (2)
must enter the Krebs Cycle
Therefore the cycle occurs twice for every glucose
molecule
Stage 4: ETC
 NADH and FADH2: release the electrons they
received during glycolysis and the Kreb’s cycle to
ETC
- proteins of the ETC transfer the electrons and use
the energy released to pump hydrogen ions (protons)
 Hydrogen ions (protons) are pumped from the
matrix to the intermembrane space
 Creates a concentration gradient
Stage 4: ETC Cont.
 Oxygen: final electron acceptor at the end of the ETC
- oxygen accepts the electrons, combines with protons
and become water
 The accumulated hydrogen ions (protons) diffuse back
into the matrix through ATP synthase complex
- The energy released from the diffusion fuels the
formation of ATP (by pumping H+ ions into
intermembrane space)
 ETC: an ongoing process
- NADH delivers electrons continuously
- FADH2 delivers lower energy electrons in different
place than NADH (cannot pump as many H+ ions)
 Electron Transport Chain animation
 Electron Transport Chain
 Electron Transport Chain
Stage 4 Cont: Chemiosmosis
 H+ ions accumulate in intermembrane space from ETC
- creates an electrochemical gradient
 H+ ions (protons) move from intermembrane space to
ATP synthase complex
- energy in gradient forces them through
 Energy released as H+ ions pass through = binds ADP
with Pi to produce ATP!
 Energy removed from 1 NADH = 3 ATP’s; 1 FADH2 = 2
ATP’s
Oxidative phosphorylation: Because the energy needed to
add the Pi group to ADP is derived from the oxidation of
a glucose molecule aka oxidative ATP synthesis
Final Points…
 ATP is now sent to the cytoplasm to be utilized by
the cell
 All stages are dependent on glycolysis for the
production of pyruvate
 Last stages are dependent on the availability of
electrons (from food– glucose) and oxygen